PrimEx Preliminary Result (short status) A. Gasparian NC A&T State University, Greensboro, NC
Three groups analyzed the data independently 0 Event selection Three groups analyzed the data independently A. Gasparian JLab, October 31, 2007
0 Differential Cross section 12C→012C Preliminary GEANT: acceptances; efficiencies … Experimental Yield per Diff. cross section A. Gasparian JLab, October 31, 2007
Fit to Extract 0 Decay Width Theoretical angular distributions smeared with experimental resolutions are fit to the data Primakoff Coherent Incoherent Interference Combined average from three groups: Γ(0) 7.93 eV 2.10%(stat.) A. Gasparian JLab, October 31, 2007
Estimated Systematic Errors (preliminary) Photon flux 1.0% Target thickness (+impurity) 0.4% Background subtraction Theoretical model error ‹1.0% Event selection 0.5% HyCal Response function Beam energy (+parameters) 11/30/20075Acceptance 0.3% Total 2.03% A. Gasparian JLab, October 31, 2007
PrimEx Preliminary Result () = 7.93eV2.1%2.0% 0 Decay width (eV) ±1.% A. Gasparian JLab, October 31, 2007
Summary to perform precision test of chiral symmetry and anomaly PrimEx collaboration has developed an experimental program to perform precision test of chiral symmetry and anomaly effects in the light pseudoscalar meson sector. A state-of-the-art high resolution experimental setup has been designed, developed and constructed in less than 5 years. The first experiment, the 0 lifetime measurement has been successfully performed in fall of 2004. Our preliminary result: Γ(0) 7.93 eV 2.10%(stat.) 2.0%(syst.) improves the uncertainty in PDG average by 2.5 times A. Gasparian JLab, October 31, 2007
Summary (cont.) The proposed 1.4% accuracy in Γ(0) can be reached with more stable data. Reach experimental program in η, η’ widths and transition form factors at 12 GeV with upgraded setup is being developed. A. Gasparian JLab, October 31, 2007